When two or more components of an engine come into contact with one another during operation of the engine, abrasion and wear of these components will occur. Also, relative motion between abutting components due to vibration will contribute to abrading action on the components. Moreover, the extremely high operating temperatures within an engine may exacerbate the wear problem. Wear of engine components can adversely impact the proper functioning of the engine. Component wear may be controlled in most applications by known methods such as lubricants, choice of materials, design features that limit motion, geometry of the components, and others. However, relative motion between components cannot be eliminated altogether and wear remains a reality for engine designers.
Prior to the occurrence of a structural or functional failure caused by wear, the suitability of components for continued service is typically determined by visual or dimensional inspection. However, there are many applications where regular inspections are not feasible because of factors including time, labor and/or disruptions due to down time. Thus, there is a need for monitoring the wear of a component while the component is in operation or without having to remove the component from its operational position.